The increasing use of credit cards has instilled new vigor into the ancient craft of pickpocketing, as the theft of one's purse or wallet, with its typical assortment of such cards can produce hundreds and even thousands of dollars in ill-gotten gains. This is particularly true if the loss of one's wallet is not detected immediately, giving the thief/thieves time to run up expensive charges before the cards can be invalidated by their owner.
Any successful theft deterrent device to be worn on a person's body or carried in a purse must operate under guidelines which anticipate a pickpocket's methods and his behavior if caught in the act or apprehended.
Pickpockets frequently work in teams of two or more individuals. The least complex, a two-man team, consists of a "stall" who intentionally attracts a would-be victim's attention while a second individual, a "pick", actually removes an article from the victim's clothing or purse. Skillfully done, the victim will not notice the theft immediately, giving the thieves an opportunity to disappear. In some cases, teams of three or more cooperate to pass the stolen article from one to another, thus further escaping detection.
Aside from detection, no pickpocket wants a confrontation with a victim. Being caught in the act, in close proximity to his victim, may panic a pickpocket, causing him to react violently in an attempt to escape. This is particularly true of alarms carried by the victim, which go off when a thief is in body contact with his victim.